Extremely small emitter (1*1 mu m/sup 2/) AlGaAs/GaAs HBT's utilizing bridged base electrode structure

A novel self-aligned structure for AlGaAs-GaAs HBTs (heterojunction bipolar transistors) with extremely small emitter sizes is presented. This structure, utilizing a bridged base electrode, successfully reduces the emitter size to 1*1 mu m/sup 2/. Despite the fact that current gain is reduced as the emitter size decreases, a current gain of more than 10 is obtained in a 1*1 mu /sup 2/ emitter HBT. In high-frequency characteristics measurements, the highest values of f/sub T/=90 GHz and f/sub max/=63 GHz are obtained in a 1*5 mu m/sup 2/ emitter HBT. The realization of a 1*1 mu m/sup 2/ emitter HBT and excellent high-frequency characteristics demonstrate the effectiveness of the proposed HBT structure.<<ETX>>